GENERAL RESEARCH GOALS

My research goals involve both pure and applied aspects. The ultimate goal is to understand the ecological processes that underlie patterns in nature, and to use these to inform management decisions in an applied conservation context. I strive to achieve a balance between research that is innovative but has direct application to important environmental issues in freshwater ecology. The common theme in my research is to understand how habitat structure influences biological processes in streams, and how biological processes are altered by human activities in a watershed.

SPECIFIC RESEARCH INTERESTS

Understanding and modelling instream flow effects on stream ecosystems – Despite decades of work, our predictive understanding of how instream flows affect fish populations, production, and community structure is at best rudimentary. I have recently become active in this area as an extension of my work in habitat limitation of fluvial fish populations. Current work and future research plans include modelling and experimental manipulations of flows in streams to compare model predictions to the true population response of fish and invertebrate prey to altered flows. This research theme is directly related to predicting the effects of climate-mediated changes in flow on lotic ecosystems.

Understanding the physiological basis of adaptive tradeoffs among the juvenile stages of stream-rearing salmonids - Although differences in morphology and habitat use amongsalmon and trout are well documented, the physiological basis of the adaptive tradeoffs that allow their co-existence in streams are poorly understood. This NSERC-funded research focuses on determining how adaptive differences in growth rate potential associated with different physiologies and life-history strategies match differences in habitat use along productivity gradients in streams.

Ecology and conservation of freshwater species at risk - Much of my recent work and graduate student supervision has focused on understanding the specific habitat requirements of listed freshwater fish species at risk, and management priorities for their conservation. This evolved in part from my term co-chairing the BC Non-Game Freshwater Fish Recovery Team, and has informed more general research and syntheses related to assessing the habitat requirements of fish and identifying critical habitat.

Cumulative impacts of development on stream ecosystems - Although regulatory frameworks in Canada and other developed nations provide protection to riparian zones and require environmental impact assessments for individual development projects, the cumulative impacts of development within a watershed are not well understood, nor are appropriate regulatory thresholds for impacts well established. I currently have one graduate student addressing this issue by relating the distribution of Salish sucker to landuse and water quality in the lower Fraser Valley, with the goal of understanding how landuse may affect persistence of this endangered species.

Bioenergetic modelling of habitat use by drift feeding fishes - I am currently using a bioenergetics-based drift-foraging model to predict patterns of growth and habitat use by juvenile salmonids in streams. Bioenergetic models can integrate the effects of changes in channel structure, temperature, and productivity (drift abundance), and therefore have the potential to generate quantitative predictions for a suite of human impacts ranging from changes in turbidity to climate-mediated effects on instream flows and temperature.

Effects of channel structure on production processes in streams – The physical habitat structure of streams drives ecological processes in running waters, and a poor understanding of geomorphological constraints to production has limited advances in this field. One of the key objectives of my research is to provide a better framework for understanding energy flow and production in streams by explicitly linking their dynamics to variation in channel structure and associated hydraulics, and using this information to inform habitat restoration.

research projects

Current Research

2017 to 2020- Developing a user-friendly modelling tool to automate production of Bioenergetics-based Habitat Suitability Curves for instream flow assessements (NSERC Collaborative Research Development Grant - with Dr. Brett Eaton in UBC Geography; $60,000 over 3 years, with support from BC Hydro and the Freshwater Fisheries Society of B.C.)

This project focuses on developing and validating user-friendly software that can be used to generate customized Habitat Suitability Curves for instream flow modelling based on the fundamental bioenergetics of energy gains and losses for drift-feeding fishes like salmonids.

The ability of fish to successfully exploit stream habitats depends on physical habitat structure, prey production, and the abundance of predators and competitors. These features form the adaptive landscape for drift-feeding fish like salmon and trout, while simultaneously constraining energy transfer to the fish trophic level. The objectives of this proposal are i) to develop a general process model relating production of invertebrate drift and juvenile drift-feeding salmonids (i.e. Pacific salmon and trout) to stream habitat structure and discharge, as a quantitative framework for modeling habitat and flow effects on juvenile salmonid production in streams; ii) to experimentally determine the adaptive tradeoffs differentiating juvenile salmonids at different taxonomic levels, with a particular emphasis on understanding the role of growth differentiation; and iii) to explore whether latitudinal constraints on herbivorous fish distribution can potentially affect energy flow and production of other functional feeding groups of fish, particularly drift-feeding fish (e.g., juvenile salmonids).

Salish sucker are a federally listed species endemic to the lower Mainland of B.C. The focus of this research is to determine the potential cumulative effects of landuse on water quality and ultimately Salish sucker populations, to inform management requirements necessary to ensure species persistence.

The focus of this research is to understand the effects of fine sediment and coarse substrate requirements of federally endangered Nooksack dace, to inform land management and habitat restoration options.

Nooksack dace are a federally listed species endemic to a small number of streams in the lower Fraser Valley. Although critical habitat has been defined for these species, summer low flows have been identified as a threat to species persistence and recovery. The objectives of this project are to quantify the relationship between flow and dace abundance, with the goal of identifying minimum instream flow needs and establishing guidelines for Nooksack dace habitat management and recovery.

Stickleback species pairs are red-listed and globally unique in that a benthic and limnetic species have evolved in the same lakes. One species pair (Hadley Lake) has already been extirpated and another has collapsed into a hybrid swarm (Enos Lake). There is an urgent need to identify critical habitat as well as to unambiguously identify threats and the cause of hybridization in Enos Lake. This project is designed to identify critical habitat through a combination of 1) habitat identification and mapping in species pairs lakes, 2) assessment of the habitat attributes that are necessary for species persistence by contrasting the attributes of species pairs lakes relative to single-species stickleback lakes, 3) assessment of fluctuations in habitat availability associated with seasonal and human-induced changes in water levels. A combination of observational studies and experiments will be used to unambiguously determine the potential roles of watershed development, changes in water quality, and introduction of crayfish as causative factors leading to hybridization in Enos Lake.

Physical habitat structure is a key ecosystem attribute that influences both basal system productivity and the transfer of energy to higher trophic levels in streams. Despite extensive research on juvenile salmon habitat relationships, the mechanisms whereby habitat structure constrains adaptations and production of drift-feeding fish remain poorly understood. This research will involve a series of experiments to evaluate the effects of physical habitat on i) adaptive constraints for drift-feeding fish, ii) transfer efficiency of energy to the fish trophic level along a longitudinal downstream gradient, and iii) bottom-up effects of habitat structure on fish production mediated through increased production of invertebrate prey. Research will be carried out in both natural and artificial stream channels, and will be used to develop and parameterize a general bioenergetic model for predicting the effects of changes in habitat, temperature, flows, and prey abundance on juvenile salmon productive capacity.

Numerous off-channel habitat structures to restore and enhance salmonid populations have been constructed in rivers and streams throughout Canada and the Pacific Northwest. However, assessment of the effectiveness of different structures and designs (in terms of juvenile salmonid growth, survival, or smolt output) has been limited. We will i) extract data from the literature to compare smolt production data from channels of contrasting design to make general inferences about how design affects production; and ii) use growth experiments and mark-recapture in focal off-channel habitats of contrasting design to assess the mechanisms whereby design affects performance of individuals.

Riparian reserve zones in British Columbia have fixed widths, beyond which timber harvesting can take place in a management zone. It is assumed that buffers of this width will, over the long term, contribute natural levels of Large Woody Debris input that maintain channel structure and fish habitat, similar to intact riparian forest. However, this does not take into account the fact that stream channels are active and stream banks naturally migrate through erosion. Over time bank erosion can lead to a significant narrowing of the portion of the buffer with intact forest available to deliver LWD to the stream channel. This project will model the effects of migration rate of stream channels in different geomorphic contexts on the long-term adequacy of present fixed-width buffers to maintaining natural LWD loadings to streams.

The monitoring and assessment of stream condition, function, and carrying capacity for fish requires application or development of appropriate assessment indices and protocols. Goals of this project are to determine which combinations of physical and biological variables are the best indicators of stream condition (in terms of capacity to support juvenile salmon), with a particular emphasis on the use of invertebrate drift abundance as an index of productive capacity, and to assess the costs and benefits of data acquisition involving varying levels of effort, providing a formal basis for optimizing information gained for effort expended.

2002 to 2003 - Modelling the effects of turbidity on growth rates of juvenile salmonids(FII $22,000)

No models exist for quantitatively estimating the impact of chronic or episodic increases in low level turbidity on juvenile salmonid growth rates. To provide a credible basis for estimating the impacts of increased turbidity, and to provide a tool for developing monitoring and assessment guidelines for forestry impacts on stream turbidity, we are developing a model for predicting the effects of chronic and episodic low-level turbidity on growth rates of stream-dwelling salmonids.

Although the general negative impacts of decreased LWD are well documented, no quantitative tools are available for directly predicting how changes in LWD input rate will affect fish abundance in small streams. We will develop a model linking riparian management (e.g. buffer width) to LWD input rates, small stream channel structure, and abundance of juvenile anadromous cutthroat trout and coho salmon. This will be done by linking recent research on juvenile cutthroat trout habitat associations (Rosenfeld and Boss 2001, Rosenfeld et al. 2000, Rosenfeld 2000) to existing (Beechie et al. 2000) and developing LWD recruitment models (Hogan 1995). The model will then serve as an interactive management tool that can be used to predict long-term impacts of different riparian management scenarios on channel structure and juvenile salmonid abundance.

Juvenile anadromous cutthroat trout rear for up to 3 years in small coastal streams. It is unclear to what degree current forest practices protect their rearing streams. Research involves a combination of synoptic surveys of cutthroat density and stream channel/habitat structure in logged and unlogged watersheds, and detailed studies of habitat choice and fitness consequences for cutthroat juveniles, including telemetry of 2 year old parr to identify habitat use during winter floods. Goals are i) to determine the importance of channels structure and hydraulic refuges associated with LWD to juvenile cutthroat fitness, particularly overwinter survival, ii) to quantitatively understand the relationship between cutthroat density and habitat structure associated with LWD, and iii) to model the impact of different riparian management strategies on LWD input rates, channel structure, and ultimately cutthroat density.